Soft hydraulics: from Newtonian to complex fluid flows through compliant conduits

Area of Science:

• Microfluidics
• Soft Matter Physics
• Fluid Mechanics

Background:

• Soft polymeric microfluidic devices offer cost-effective, disposable platforms for biological and chemical analyses.
• The mechanical compliance of these devices, initially a material side-effect, is now a key feature enabling novel functionalities.
• Understanding the interplay between fluid dynamics and deformable boundaries is crucial for optimizing microfluidic systems.

Purpose of the Study:

• To review recent advancements in the mechanistic understanding of non-Newtonian fluid flow within deformable microfluidic conduits.
• To explore the physics governing the interaction between complex fluids and their soft boundaries.
• To highlight key experimental findings, applications, and modeling principles in soft hydraulics.

Main Methods:

• Review of experimental results and theoretical principles.
• Analysis of fluid-structure interactions in soft microfluidic systems.
• Discussion of physics-based modeling approaches for deformable conduits.

Main Results:

• Detailed examination of shear-dependent viscosity in non-Newtonian fluids.
• Analysis of hydrodynamic pressure gradients and conduit elastic responses (deformation, bulging).
• Exploration of the impact of conduit geometry and dimensionless groups on fluid-structure interaction.

Conclusions:

• Significant progress has been made in understanding soft hydraulics at the microscale.
• The field integrates non-Newtonian fluid mechanics, soft matter physics, and microfluidics.
• Open challenges and future research directions are identified for soft microfluidic systems.